| /* SPARC-specific values for a.out files |
| |
| Copyright (C) 2001-2021 Free Software Foundation, Inc. |
| |
| This program is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3 of the License, or |
| (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program; if not, write to the Free Software |
| Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, |
| MA 02110-1301, USA. */ |
| |
| /* Some systems, e.g., AIX, may have defined this in header files already |
| included. */ |
| #undef TARGET_PAGE_SIZE |
| #define TARGET_PAGE_SIZE 0x2000 /* 8K. aka NBPG in <sys/param.h> */ |
| /* Note that some SPARCs have 4K pages, some 8K, some others. */ |
| |
| #define SEG_SIZE_SPARC TARGET_PAGE_SIZE |
| #define SEG_SIZE_SUN3 0x20000 /* Resolution of r/w protection hw */ |
| |
| #define TEXT_START_ADDR TARGET_PAGE_SIZE /* Location 0 is not accessible */ |
| #define N_HEADER_IN_TEXT(x) 1 |
| |
| /* Non-default definitions of the accessor macros... */ |
| |
| /* Segment size varies on Sun-3 versus Sun-4. */ |
| |
| #define N_SEGSIZE(x) (N_MACHTYPE(x) == M_SPARC? SEG_SIZE_SPARC: \ |
| N_MACHTYPE(x) == M_68020? SEG_SIZE_SUN3: \ |
| /* Guess? */ TARGET_PAGE_SIZE) |
| |
| /* Virtual Address of text segment from the a.out file. For OMAGIC, |
| (almost always "unlinked .o's" these days), should be zero. |
| Sun added a kludge so that shared libraries linked ZMAGIC get |
| an address of zero if a_entry (!!!) is lower than the otherwise |
| expected text address. These kludges have gotta go! |
| For linked files, should reflect reality if we know it. */ |
| |
| #define N_SHARED_LIB(x) ((x)->a_entry < TEXT_START_ADDR \ |
| && (x)->a_text >= EXEC_BYTES_SIZE) |
| |
| /* This differs from the version in aout64.h (which we override by defining |
| it here) only for NMAGIC (we return TEXT_START_ADDR+EXEC_BYTES_SIZE; |
| they return 0). */ |
| |
| #define N_TXTADDR(x) \ |
| (N_MAGIC(x)==OMAGIC? 0 \ |
| : (N_MAGIC(x) == ZMAGIC && (x)->a_entry < TEXT_START_ADDR)? 0 \ |
| : TEXT_START_ADDR+EXEC_BYTES_SIZE) |
| |
| /* When a file is linked against a shared library on SunOS 4, the |
| dynamic bit in the exec header is set, and the first symbol in the |
| symbol table is __DYNAMIC. Its value is the address of the |
| following structure. */ |
| |
| struct external_sun4_dynamic |
| { |
| /* The version number of the structure. SunOS 4.1.x creates files |
| with version number 3, which is what this structure is based on. |
| According to gdb, version 2 is similar. I believe that version 2 |
| used a different type of procedure linkage table, and there may |
| have been other differences. */ |
| bfd_byte ld_version[4]; |
| /* The virtual address of a 28 byte structure used in debugging. |
| The contents are filled in at run time by ld.so. */ |
| bfd_byte ldd[4]; |
| /* The virtual address of another structure with information about |
| how to relocate the executable at run time. */ |
| bfd_byte ld[4]; |
| }; |
| |
| /* The size of the debugging structure pointed to by the debugger |
| field of __DYNAMIC. */ |
| #define EXTERNAL_SUN4_DYNAMIC_DEBUGGER_SIZE (24) |
| |
| /* The structure pointed to by the linker field of __DYNAMIC. As far |
| as I can tell, most of the addresses in this structure are offsets |
| within the file, but some are actually virtual addresses. */ |
| |
| struct internal_sun4_dynamic_link |
| { |
| /* Linked list of loaded objects. This is filled in at runtime by |
| ld.so and probably by dlopen. */ |
| unsigned long ld_loaded; |
| |
| /* The address of the list of names of shared objects which must be |
| included at runtime. Each entry in the list is 16 bytes: the 4 |
| byte address of the string naming the object (e.g., for -lc this |
| is "c"); 4 bytes of flags--the high bit is whether to search for |
| the object using the library path; the 2 byte major version |
| number; the 2 byte minor version number; the 4 byte address of |
| the next entry in the list (zero if this is the last entry). The |
| version numbers seem to only be non-zero when doing library |
| searching. */ |
| unsigned long ld_need; |
| |
| /* The address of the path to search for the shared objects which |
| must be included. This points to a string in PATH format which |
| is generated from the -L arguments to the linker. According to |
| the man page, ld.so implicitly adds ${LD_LIBRARY_PATH} to the |
| beginning of this string and /lib:/usr/lib:/usr/local/lib to the |
| end. The string is terminated by a null byte. This field is |
| zero if there is no additional path. */ |
| unsigned long ld_rules; |
| |
| /* The address of the global offset table. This appears to be a |
| virtual address, not a file offset. The first entry in the |
| global offset table seems to be the virtual address of the |
| sun4_dynamic structure (the same value as the __DYNAMIC symbol). |
| The global offset table is used for PIC code to hold the |
| addresses of variables. A dynamically linked file which does not |
| itself contain PIC code has a four byte global offset table. */ |
| unsigned long ld_got; |
| |
| /* The address of the procedure linkage table. This appears to be a |
| virtual address, not a file offset. |
| |
| On a SPARC, the table is composed of 12 byte entries, each of |
| which consists of three instructions. The first entry is |
| sethi %hi(0),%g1 |
| jmp %g1 |
| nop |
| These instructions are changed by ld.so into a jump directly into |
| ld.so itself. Each subsequent entry is |
| save %sp, -96, %sp |
| call <address of first entry in procedure linkage table> |
| <reloc_number | 0x01000000> |
| The reloc_number is the number of the reloc to use to resolve |
| this entry. The reloc will be a JMP_SLOT reloc against some |
| symbol that is not defined in this object file but should be |
| defined in a shared object (if it is not, ld.so will report a |
| runtime error and exit). The constant 0x010000000 turns the |
| reloc number into a sethi of %g0, which does nothing since %g0 is |
| hardwired to zero. |
| |
| When one of these entries is executed, it winds up calling into |
| ld.so. ld.so looks at the reloc number, available via the return |
| address, to determine which entry this is. It then looks at the |
| reloc and patches up the entry in the table into a sethi and jmp |
| to the real address followed by a nop. This means that the reloc |
| lookup only has to happen once, and it also means that the |
| relocation only needs to be done if the function is actually |
| called. The relocation is expensive because ld.so must look up |
| the symbol by name. |
| |
| The size of the procedure linkage table is given by the ld_plt_sz |
| field. */ |
| unsigned long ld_plt; |
| |
| /* The address of the relocs. These are in the same format as |
| ordinary relocs. Symbol index numbers refer to the symbols |
| pointed to by ld_stab. I think the only way to determine the |
| number of relocs is to assume that all the bytes from ld_rel to |
| ld_hash contain reloc entries. */ |
| unsigned long ld_rel; |
| |
| /* The address of a hash table of symbols. The hash table has |
| roughly the same number of entries as there are dynamic symbols; |
| I think the only way to get the exact size is to assume that |
| every byte from ld_hash to ld_stab is devoted to the hash table. |
| |
| Each entry in the hash table is eight bytes. The first four |
| bytes are a symbol index into the dynamic symbols. The second |
| four bytes are the index of the next hash table entry in the |
| bucket. The ld_buckets field gives the number of buckets, say B. |
| The first B entries in the hash table each start a bucket which |
| is chained through the second four bytes of each entry. A value |
| of zero ends the chain. |
| |
| The hash function is simply |
| h = 0; |
| while (*string != '\0') |
| h = (h << 1) + *string++; |
| h &= 0x7fffffff; |
| |
| To look up a symbol, compute the hash value of the name. Take |
| the modulos of hash value and the number of buckets. Start at |
| that entry in the hash table. See if the symbol (from the first |
| four bytes of the hash table entry) has the name you are looking |
| for. If not, use the chain field (the second four bytes of the |
| hash table entry) to move on to the next entry in this bucket. |
| If the chain field is zero you have reached the end of the |
| bucket, and the symbol is not in the hash table. */ |
| unsigned long ld_hash; |
| |
| /* The address of the symbol table. This is a list of |
| external_nlist structures. The string indices are relative to |
| the ld_symbols field. I think the only way to determine the |
| number of symbols is to assume that all the bytes between ld_stab |
| and ld_symbols are external_nlist structures. */ |
| unsigned long ld_stab; |
| |
| /* I don't know what this is for. It seems to always be zero. */ |
| unsigned long ld_stab_hash; |
| |
| /* The number of buckets in the hash table. */ |
| unsigned long ld_buckets; |
| |
| /* The address of the symbol string table. The first string in this |
| string table need not be the empty string. */ |
| unsigned long ld_symbols; |
| |
| /* The size in bytes of the symbol string table. */ |
| unsigned long ld_symb_size; |
| |
| /* The size in bytes of the text segment. */ |
| unsigned long ld_text; |
| |
| /* The size in bytes of the procedure linkage table. */ |
| unsigned long ld_plt_sz; |
| }; |
| |
| /* The external form of the structure. */ |
| |
| struct external_sun4_dynamic_link |
| { |
| bfd_byte ld_loaded[4]; |
| bfd_byte ld_need[4]; |
| bfd_byte ld_rules[4]; |
| bfd_byte ld_got[4]; |
| bfd_byte ld_plt[4]; |
| bfd_byte ld_rel[4]; |
| bfd_byte ld_hash[4]; |
| bfd_byte ld_stab[4]; |
| bfd_byte ld_stab_hash[4]; |
| bfd_byte ld_buckets[4]; |
| bfd_byte ld_symbols[4]; |
| bfd_byte ld_symb_size[4]; |
| bfd_byte ld_text[4]; |
| bfd_byte ld_plt_sz[4]; |
| }; |